Bearing construction for gyroscopes and like instruments



June 27, 1961 BEARING CONSTRUCTION FOR GYROSCOPES AND LIKE INSTRUMENTSOriginal Filed Oct. 24, 1958 G. L. JONES 2,990,222

j INVENTOR. My ,mfe c ziz 0 w United States 3 Claims. (Cl. 308-194) Thisinvention relates to an improved bearing for gyroscopes and otherinstruments wherein the running clearances and friction must be apractically irreducible This application is a division of my co-pendingapplication Serial No. 769,426, filed October 24, 1958.

In the art of gyroscopes and gyroscopic instruments, it is well knownthat torque exerted by bearing friction and lack of alignment due toexcessive clearances can introduce errors of precession therebyinterfering with the basic operation of a gyroscope namely, that ofproviding an absolute reference in space. While some measure'of' driftdue to hearing deficiencies may be tolerated it is necessary that thedeparture of the gyroscope from a predetermined reference be regarded asa pure function of defined displacing forces acting in defineddirecfions and, therefore, when drift is to be reckoned with, the effectthereof on the system of which the gyroscope forms a part must beanticipated and corrected for accordingly. With the advent of guidedmissiles the demand for greater accuracy in the response of gyroscopeshas taken on increased importance as the effect of drift may introduceerrors which may be translated into a miss of several miles at thetarget. Even though drift is composed of several factors a predominantone is bearing'friction run-out due to excessive clearance in thebearings. If a bearing is not sufiiciently accurate in the fit of itsseveral parts attempts are made to reduce the play by take-up meanswhich only aggravate the condition, since the error due to eccentricityis then converted into friction.

My invention has, therefore, as its principal object the provision of abearing capable of being manufactured with far greater accuracy thanprior bearings.

Another object is to provide a bearing as aforesaid wherein the pivotforming the end of the shaft which the bearing supports is so configuredas to substantially eliminate dimensional changes due to cold working ofthe parts.

'Still another object is to provide a bearing in which play may bereduced by adjustment but without any appreciable proportionate increasein the friction.

Another object is to provide a bearing as aforesaid wherein a pivot partsupported on antifriction balls may be axially bored for the passage ofvarious members, e.g. a tube conducting compressed air for driving therotor and for other purposes. An additional object is to provide abearing as aforesaid fora rate gyroscope which will permit the passageaxially therethrough of the elongated, torsionally deformable elementcurrently employed for biasing the gimbal with respect to the frame andwhich will, concurrently, relieve the element from the weight of thegimbal and the parts carried thereby.

Another object is to provide a bearing as aforesaid capable of axiallyaccommodating a plurality of electrical conductors forming connectionsbetween one gimbal and another gimbal or the frame of the gyroscope.

Other objects and advantages of the invention will become apparent fromthe ensuing description which, taken with the accompanying drawing,discloses certain preferred embodiments of the invention.

atent Q In this drawing:

FIG. 1 is an axial cross section of a bearing in accordance with theinvention;

FIG. 2 is a cross section taken on the line of 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 1 of an alternative embodiment; and

FIG. 4 is a view similar to FIG. 1 of another alternative.

Broadly regarded the invention comprises a mounting on one of therelatively rotatable parts to receive a male bearing member providedwith a spherical surface and a race on the other of the parts carryingan annular array of balls supporting the male member togetherconstituting an anti-friction bearing. At this juncture it should benoted that where herein one of the parts which the bearing serves isreferred to as the fixed part and the other as the rotatable part theseterms are intended to be relative since their functions, as concerns theenvironment of the invention, are interchangeable. Moreover the termrotatable is intended to comprehend movement about an axis over smallangles in both directions from a zero position, as would be the case ina rate gyroscope. The spherical surface of the male member is tangentialto the plurality of balls and is of such radius as to transmit the loadof the rotatable part to the balls and thence to the race for optimumsupport and degree of wear. Any suitable means may be provided forendwise adjustment to reduce the running clearances to a minimumconsistent with minimum friction. Thus the support between thespherically-surfaced member and the balls is constituted as the severalpoints of tangency of one spherical surface with a plurality of other,identical spherical surfaces. The circle of centers of the plurality ofballs and their diameter, and the diameter of the contacting sphericalsurface are all so selected as to define an internal clearance space forpassage of elements passing axially through the bearing, e.g. a tubecarrying compressed air, a plurality of electrical conductors, a gimbalbiasing element, etc. The invention bearing also enables rapid assemblyand disassembly of the two relatively rotatable parts without the needof dislodging press-fitted parts and the hazard of deformation such stepentails. Moreover the invention hearing, by reason of the tangentialrelation between the spherical member and balls is self-aligning.

Adverting to the drawing I have shown, by way of example, several modesof carrying the invention into practice as applied particularly togyroscopes. In FIG. 1 there is shown a portion of a fixed frame 10 whichmay, alternatively, be regarded as a movable gimbal, together with aportion of a gimball 11. It will be understood that the representationof FIG. 1 is of one bearing and that its companion bearing is axiallyaligned therewith. A recess 13 is formed in the frame 10 to receive, ina press fit, a seat 15 provided with a limiting flange 16. The outer endof the seat 15 is bored at 17 to receive the element 21 which may be atrue sphere or provided with a spherical Zone 'at the working region.This latter is preferably inserted into the bore 17 with a light pressfit in order to avoid deformation thereof and merely to retain the sameagainst falling out when the parts are in stages of disassembly.Although, for convenience, the element 21 is shown as a sphere it willbe understood that only a portion thereof exposed beyond the seat 15partakes in the bearing function. Accordingly that portion of theelement within the seat 15 may be otherwise formed, e.g. cylindrical,whereby to position an axial hole through the element.

The gimbal 11 is provided with a cylindrical recess 25 into which a race26 is press fitted. Race 26 has a segmentally toroidal groove 27 toreceive, in rolling relation, a plurality of balls 28 with which thespherical surface of the element 21 is in rolling contact. The diameterof the balls 28 and of the spherical surface of the element 21 are soselected as to provide a force component on each ball in a directionaccommodating both radial and axial thrust, e.g. a component at an angleof 60 to the axis of rotation of the gimbal 11. If it is desired toprovide greater accommodation of radial thrust than axial thrust or viceversa the relative radii of the spherical surface of the element 21 andof the balls 28 are modified accordingly to shift the circle of tangentpoints and therefore the direction of the resultant force componentsthrough that circle. Thus the invention bearing affords greatflexibility in its application without affecting the principles involvedor the function thereof. It will be understood, of course, that thespherical element and the balls are of hardened steel or equivalent suchas tungsten carbide.

The invention bearing possesses important utility where it is desired toprovide a passage through the bearing for a driving medium, e.g.compressed air or air under suction. For example, in FIG. 1, compressedair is to be admitted to a chamber enclosing the gyroscope rotor from asource exterior to the frame 10. Accordingly, assuming the source to bea port 31, the seat is bored at 32 to receive a feed tube 33 which thenpasses through a bore 35 in the element 21, thence through clearanceholes 36 and 37 in the race 26 and gimbal 11 to terminate close to aport 38 feeding to the rotor enclosure (not shown). The bore 35 mayreceive the tube 33 with a loose or tight fit as desired. The end of thetube 33 may be terminated at the port 38 with only running clearanceremaining. Thus compressed air may beconducted through the bearingwithout, in any way, alfecting the basic organization thereof.

Another embodiment of the invention is seen in FIG. 3 which, whiledifierent in minor details of construction, includes the bearingcomponents described in connection with FIG. 1. In this case electricalcomponents carried on the gimbal 11a are fed by or feed to, a pluralityof conductors 41 which are passed through a protecting and guiding tube42 of electrically-insulating or other material similar to the tube 33.At its outer end the tube 42 carries a plurality of suitably insulatedslip rings 43 upon which a plurality of brushes 44 may wipe. In thisexample it is to be observed that the element 21 is spherical and isreceived on a seat 46 which is a spherical zone congruent with thesurface of the element 21. If desired the latter may be sweated to itsseat while held aligned by a suitable mandrel.

A further form of the invention is shown in FIG. 4 wherein the bearingsupports the gimbal 11b of a rate gyroscope. In this instrument thegimbal 11b is permitted only an oscillating movement through smallangles of displacement and is restored to zero by means of a torsionallydeformable rod or wire 51 fixed at its ends in the frame 10b and gimbal11b respectively, as is understood in this art. Since, in most cases,the rod or wire 51 is, in general, incapable of carrying the weight ofthe gimbal, rotor and the parts appertaining thereto separate bearingsare provided. The invention bearing is ideally suited to thisenvironment since the rod or wire 51 may be passed axially therethroughas explained hereinabove. In this way the rod or wire 51 is not calledupon to carry either radial or axial thrust and may therefore performits basic function as a restoring spring independently of extraneousforces.

It has been found that the invention bearing has minimum friction at aclearance of from 0.000025" to 0.000050 as compared to 0.0003" for aconventional ball bearing. Thus precessive errors due to weight shiftare substantially reduced.

Inasmuch as the dimensions of the element 21 are, in practice, extremelysmall, say /2" in diameter, I have found that the diametrical boretherethrough, when required, may be obtained best by the method ofelectrolytic decomposition which is without adverse effect on thesphericity or the hardened surface of the element- While I have shownparticular embodiments of my invention, it will be understood, ofcourse, that I do not Wish to be limited thereto since manymodifications may be made and I, therefore, contemplate by the appendedclaims to cover any such modifications as fall within the true spiritand scope of my invention.

I claim:

1. In a gyroscope or like instrument which includes a framework, agimbal supported on said framework for rotation in both directionsthrough small angles limited by the elasticity of a torsionallydeformable element secured at its ends to the framework and gimbalrespectively and having a twist axis coaxial with the axis of rotationof the gimbal, means for rotatably supporting the gimbal on saidframework comprising an annular race carried on one of the framework andgimbal, a plurality of balls retained in annular array in said race forrotation therein, an axially bored member having a spherical surfacefixed to the other of the framework and gimbal, as the case may be,coaxial with the axis of rotation of the gimbal, said surface beingtangential to all of said balls for rotatable relation therewith, saidballs together defining a substantially circular opening coaxial withsaid axis, the torsional element passing through said opening and bore,the secured ends of said torsionally deformable element being securedbeyond each end of said gimbal supporting means.

2. The improvement in accordance with claim 1 wherein the axial bore ofsaid member clears said torsionally deformable element whereby the sameis free of any restraining or deforming forces exerted by said gimbalsupporting means.

3. The improvement in accordance with claim l wherein said sphericalsurface is part of a sphere and there is provided seating means forreceiving the sphere and carrying the same on the framework and gimbal,as the case may be.

References Cited in the file of this patent UNITED STATES PATENTS1,647,419 Tanner Nov. 1, 1927 2,351,890 Turner June 20, 1944 2,766,625Swanson Oct. 16, 1956 2,809,029 Christoph Oct. 8, 1957

